More than 7,000 May 205 calls have changed hands in a strong buying pattern today, led by a print of 5,568 that went for $2.55, according to optionMONSTER's Heat Seeker real-time tracking system. The volume was far above the strike's open interest of 1,065 contracts before the session began, clearly showing that today's trading represents new purchases.

The MDY is up 1.21 percent to $203.44 this afternoon. The exchange-traded fund tracks the performance of the S&P MidCap 400 Index, which includes diverse holdings such as drug maker Regeneron Pharmaceuticals, oil refiner HollyFrontier, and railroad operator Kansas City Southern.

Today's long calls, which lock in the price where traders can buy the stock no matter how high it rises, are looking for the MDY to gain roughly 2 percent or more in the next month. These options could be sold earlier at a profit if premiums rise with a rally before then, but the contracts will expire worthless if the the stock remains below the $205 strike price. (See our Education section)

Total option volume in the MDY has already exceeded 9,800 contracts today, compared with a full-session average of 4,039 in the last month. Calls outnumber puts by 4 to 1 so far, a reflection of the day's bullish sentiment.

optionMONSTER® provides stock market insight, advanced options education, and actionable trade ideas to meet the needs of do-it-yourself investors. After spending decades in the trading pits of Chicago, Jon 'DRJ' and Pete Najarian founded the company in 2005 to help people better manage their own investment portfolios.